Automatically controlling operation of a BRAS device based on encapsulation information

ABSTRACT

A technique controls operation of a BRAS device. The technique involves extracting encapsulation information from a communications exchange between a CPE device and an external server device (e.g., a DHCP server). The communications exchange passes through the BRAS device and a DSLAM device. The technique further involves storing the encapsulation information in local memory of the BRAS device, and controlling a flow of a downstream communication passing through the BRAS device and the DSLAM device toward the CPE device based on the encapsulation information stored in the local memory of the BRAS device. Accordingly, the BRAS device is well suited for performing ATM overhead accounting as well as shaping and policing downstream traffic.

BACKGROUND

A Digital Subscriber Line Access Multiplexer (DSLAM) is a network devicethat is capable of receiving upstream signals from multiple subscribers(e.g., Customer Premises Equipment or CPE) and aggregating theseupstream signals onto backbone switching equipment such as a BroadbandRemote Access Server (BRAS) of a Network Service Provider (NSP). In atypical CPE/DSLAM/BRAS layout, the communications between the CPE andDSLAM is ATM-based (e.g., Point-to-Point over asynchronous transfer modeor PPPoA) while the communications between the DSLAM and the BRAS isgenerally packet-based.

A number of standards are available which enable encapsulation of LocalArea Network (LAN) and Wide Area Network (WAN) protocols over ATM (e.g.,AAL5, AAL3, RBE, PPPoE/PPPoA, IPoA, IMA, and so on). Such standardsprovide different alternatives for integrating ATM communications intoexisting WAN and/or LAN communications.

Moreover, since packets can be quite large (e.g., 8,000 bytes in length)but ATM cells are fixed at 53 bytes in length (i.e., the first 5 bytesbeing header information and the remaining 48 bytes being reserved fordata), the overhead cost of using ATM is relatively high. That is,relatively speaking, the 5-byte header is an excessive overhead cost andcuts into the amount of data that can be transferred between the CPE andthe DSLAM. Along these lines, the term “ATM cell tax” is often used todescribe the overhead cost imposed by ATM cells.

Nevertheless, providers typically offer Quality of Service (QoS) supportto their subscribers, and thus intelligently apportion data within thefixed 48-byte data fields of ATM cells in a hands-on manner. One way toaccomplish this hands-on apportionment is for the providers to manuallyconfigure BRAS equipment to control the downstream flow of networktraffic with knowledge that packetized communications between the BRASand the DSLAM will then face ATM encapsulation from the DSLAM to theCPE. In particular, technicians of the providers manually enterknowledge of the downstream protocols in use from the DSLAM to the CPE(e.g., PPPoA) and a conversion scheme which appropriately accounts forthe ATM cell tax. Such operation involves the technicians entering suchinformation through a command line interface (CLI) of the BRASequipment.

For example, if the BRAS receives a 64-byte packet en route to the DSLAMand if the BRAS knows that the DSLAM will split the 64-byte packet intotwo 53-byte ATM cells, the BRAS can impose a level of flow control whichis commensurate for two 53-byte ATM cells (i.e., 106 bytes in total).Accordingly, the BRAS may impose a scheme for shaping and policing thedownstream flow which is more favorable to the DSLAM. As a result, theoperation of the DSLAM can be improved (e.g., less dropped packets,enhanced ability to preserve packet priorities, etc.). It should beunderstood that different encapsulations will have different overheadand thus require different computations.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages will beapparent from the following description of particular embodiments of theinvention, as illustrated in the accompanying drawings in which likereference characters refer to the same parts throughout the differentviews. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of various embodiments of theinvention.

FIG. 1 is a block diagram of a system having a BRAS device configured tooperate based on encapsulation information obtained from communicationsflowing through a DSLAM device and the BRAS device.

FIG. 2 is a block diagram of the DSLAM device of FIG. 1.

FIG. 3 is a block diagram of the BRAS device of FIG. 1.

FIG. 4 is a flowchart of a procedure performed by the BRAS device ofFIG. 3 in accordance with a first operating mode.

FIG. 5 is a flowchart of a procedure performed by the BRAS device ofFIG. 3 in accordance with a second operating mode.

FIG. 6 is a timing diagram illustrating the DHCP information exchangebetween various devices during the procedure of FIG. 5.

DETAILED DESCRIPTION Overview

Unfortunately, the above-described conventional approach, which involvestechnicians manually configuring BRAS equipment to account for aparticular ATM encapsulation scheme, suffers from a variety ofdeficiencies. For example, it is extremely burdensome for technicians tomanually configure the BRAS equipment through a CLI. That is, eachconfiguration endeavor is labor intensive and susceptible to humanerror. Furthermore, such manual configuring may significantly slow downthe process of adding new subscribers. Furthermore, whenever theencapsulation between the DSLAM and the subscriber (CPE) changes, thetechnicians of the providers need to manually update the knowledge ofthe changed encapsulation in the BRAS device.

In contrast to the above-described conventional approach to manuallyconfiguring BRAS equipment to account for a particular ATM encapsulationscheme, an improved technique involves automatically controllingoperation of a BRAS device (i.e., a data communications deviceconfigured to perform BRAS operations) based on encapsulationinformation obtained from communications flowing through a DSLAM device(i.e., a data communications device configured to perform DSLAMoperations) and the BRAS device. Such encapsulation information (e.g.,the particular type or types of ATM encapsulation) is easily acquired bythe BRAS device (e.g., from a exchange of Dynamic Host ConfigurationProtocol or DHCP messages between the CPE and a DHCP server passingthrough the DSLAM and BRAS devices) thus removing the burden of atechnician having to configure the BRAS device manually. Accordingly,the time delays, human error risks and related burdens associated with atechnician manually configuring the BRAS device are alleviated.

One embodiment is directed to a method of controlling operation of aBRAS device. The method includes extracting encapsulation informationfrom a communications exchange between a CPE device and an externalserver device (e.g., a DHCP server). The communications exchange passesthrough the BRAS device and a DSLAM device. The method further includesstoring the encapsulation information in local memory of the BRASdevice, and controlling a flow of a downstream communication passingthrough the BRAS device and the DSLAM device toward the CPE device basedon the encapsulation information stored in the local memory of the BRASdevice. Accordingly, the BRAS device is well suited for performing ATMoverhead accounting as well as shaping and policing downstream traffic.

Description of Example Embodiments

FIG. 1 shows a system 20 having a BRAS device configured to operatebased on encapsulation information obtained from communications flowingthrough a DSLAM device and the BRAS device. The system 20 includesmultiple subscribers 22(1), 22(2), . . . (collectively, subscribers 22),a DSLAM device 24, a BRAS device 26, and a DHCP server 28. Thesubscribers 22, the DSLAM device 24, the BRAS device 26, the DHCP server28 as well as one or more other devices 30 are configured to communicatewith each other through a communications fabric 32 (e.g., copper wire,fiber optic cable, wireless medium, related data communications devices,combinations thereof, etc.). It should be understood that othercomponents (e.g., firewalls, routers, switches, bridges, gateways, etc.)can be considered to belong to the system 20 as well.

Each subscriber 22 is customer premises equipment which is configured toacquire a network address 34 using DHCP. In particular, each subscriber22 is configured to operate as a DHCP client that obtains and renews anIP network address from the DHCP server 28. To facilitate suchoperation, the DSLAM device 24 includes an enhanced DHCP relay agent36(D), and the BRAS device 26 includes another enhanced DHCP relay agent36(B). The DHCP relay agents 36(D), 36(B) (collectively, DHCP relayagents 36) are configured to relay DHCP messages 38 from the CPEupstream to the DHCP server 28. The DHCP relay agents 36 are furtherconfigured to relay DHCP messages 40 from the DHCP server 28 downstreamto the CPE.

Moreover, the DHCP relay agent 36(D) is configured to receive upstreamDHCP messages 38(0) and add a “Relay Agent Information” option (e.g.,option code “82” information) thus generating DHCP messages 38(1).Similarly, the DHCP relay agent 36(B) are configured to receive upstreamDHCP messages 38(1) and add a “Relay Agent Information” option thusgenerating DHCP messages 38(2). A description of DHCP options isprovided in a publication entitled “RFC 2132—DHCP Options and BOOTPVendor Extensions” by S. Alexander and R. Droms, dated March 1997, theteachings of which are hereby incorporated by reference in theirentirety.

Along these lines and as will be explained in further details later, theDHCP relay agent 36(D) is configured to participate in the addition ofencapsulation information within DHCP communications through the system20, while the DHCP relay agent 36(B) is configured to automaticallyacquire the encapsulation information from the DHCP communications andthen shape and police downstream traffic based on the acquiredencapsulation information. In contrast to conventional approaches forATM overhead accounting, such operation by the enhanced DHCP relayagents 36 occurs dynamically and without the need for any manualadjustment thus saving substantial set-up time and effort. At thispoint, it should be understood that a suitable network topology for thesystem 20 is that of WT-101 where the DSLAM device 24 operates as anaccess node and is configured to add DHCP relay agent informationcontaining information on the port (e.g., DSL line) of the subscriber 22requesting an IP network address 34.

To obtain an IP network address 34, the subscriber 22 outputs DHCPclient messages 38 (e.g., DHCPDISCOVER, DHCPREQUEST, etc.) to the DHCPserver 28. The DHCP server 28 responds to the DHCP client messages 38from the subscriber 22 with DHCP server messages 40 (e.g., DHCPOFFER,DHCPACK, etc.). Some or all of these DHCP messages 38, 40 between thesubscriber 22 and the DHCP server 28 (collectively, DHCP signals 42) maybe forwarded and embellished by the DHCP relay agents 36(D), 36(B)(collectively, relay agents 36). In this manner, IP addresses arerobustly and reliably assigned and managed within the system 20. Asuitable technique for exchanging DHCP information which involvesmultiple DHCP relay agents is described in U.S. patent application Ser.No. 11/495,273, entitled “TECHNIQUES FOR EXCHANGING DHCP INFORMATIONAMONG DHCP RELAY AGENTS AND DHCP SERVERS”, the entire teachings of whichare hereby incorporated by reference.

Once the subscribers 22 have obtained network addresses from the DHCPserver 28, the subscribers 22 are then well-equipped to exchange signals44 with a variety of external devices (e.g., the device 30). Forexample, the subscribers 22 can then operate as subscriber edge devicesthat obtain web content from various web servers over the Internet.

It should be understood that, within the flow of the DHCP signals 42 isencapsulation information which identifies the type of ATM encapsulationcarried out for communications 46 between the subscribers 22 and theDSLAM device 24 (i.e., the particular protocols utilized incommunications flowing through the final leg extending between the DSLAMdevice 24 and CPE). The BRAS device 26 is configured to (i)automatically obtain such information from the DHCP signals 42 and then(ii) control the manner in which communications 48 flow between the BRASdevice 26 and the DSLAM device 24 based on that information (i.e., thecommunications leg between the BRAS device 26 and the DSLAM device 24).In particular, the BRAS device 26 is configured to determine theparticular ATM cell tax incurred due to ATM encapsulation for the edgecommunications 46 and thus throttle the edge communications 46 in thedownstream direction to preserve QoS to the subscribers 22. Such ATMoverhead accounting enhances subscriber QoS (e.g., provides less droppedpackets, enhances the ability of the system 20 to preserve packetpriorities, etc.) but without the burden of forcing technicians tomanually configure a BRAS as in conventional approaches.

For example, based on the encapsulation information automaticallygathered by monitoring the DHCP signals 42, suppose that the BRAS device26 determines that the type of ATM encapsulation employed between thesubscribers 22 and the DSLAM device 24 results in 53-byte ATM celltransmissions with 5-byte headers. That is, the DSLAM device 24 willsplit a 64-byte packet from the BRAS device 26 into two 53-byte ATMcells. Armed with this knowledge, the BRAS device 26 is capable ofcontrolling the rate of data flowing in the downstream direction to theCPE (e.g., throttling packets, dropping lower priority packets,combining or dividing packets, classifying and queuing packets, etc.) sothat the subscribers 22 properly receive their prescribed QoS. Furtherdetails will now be provided with reference to FIG. 2.

FIG. 2 is a detailed view 60 of the DSLAM device 24. The DSLAM device 24includes a network interface 62, a DSLAM module 64 and the DHCP relayagent module 66. The DHCP relay agent module 66 corresponds to the DHCPrelay agent 36(D) in FIG. 1. The DSLAM module 64 is configured toperform DSLAM operations such as aggregate communications of themultiple subscribers 22. The DHCP relay agent 66 is configured toperform DHCP relay agent operations (e.g., operate as an intermediatedevice between a DHCP client and a DHCP server for relaying DHCPmessages).

In some arrangements, the DSLAM module 64 and the DHCP relay agentmodule 66 operate on separate designated circuits within the DSLAMdevice 24. In other arrangements, the DSLAM module 64 and the DHCP relayagent module 66 run on the same circuitry (e.g., as different processesor threads on the same set of processors). In all of these arrangements,the DSLAM module 64 and the DHCP relay agent module 66 are configured tocommunicate with each other (e.g., via one or more internalcommunications buses, via one or more inter-process communicationsschemes, via operating system and/or application programming interfaces,combinations thereof, etc.).

In the manner of traditional DHCP relay agents, the DHCP relay agentmodule 66 conveys the DHCP messages 42 between the subscribers 22 andthe DHCP server 28 (also see FIG. 1). However, the DHCP relay agentmodule 66 is further configured to add encapsulation information asrelay agent information under option code “82” (e.g., also see RFC 2132)to the upstream DHCP messages 38 and to extract such relay agentinformation from corresponding downstream DHCP messages 40. Along theselines, the network interface 62 is configured to receive a DHCP clientmessage 38(0) from a subscriber 22 and provide the DHCP client message38(0) to the DHCP relay agent module 66. The DHCP relay agent 66 isconfigured to then send a request 68 to the DSLAM module 64 asking forthe type or types of encapsulation employed for the communications 46between the subscribers 22 and the DSLAM device 24 (FIG. 1). It will beappreciated that a variety of protocols are available for use such asAAL5, AAL3, RBE, PPPoE/PPPoA, IPoA, IMA, and so on. Upon receipt of aresponse 70 indicating the type or types of encapsulation carried outfor the communications 46, the DHCP relay agent 66 inserts one or moreidentifiers which identifies the type or types of encapsulation ascontents of a relay agent information option (e.g., option code “82”)within the DHCP client message 38(1) and then provides this embellishedDHCP client message 38(1) to the network interface 62 which forwards theDHCP message 38(1) upstream.

It should be understood that the DSLAM module 64 is configured tocontinue to provide the encapsulation information within subsequent DHCPmessages from the same subscribers 22 (i.e., DHCP clients) during IPaddress renewal operations. That is, when the subscribers 22 send newDHCP messages 36 to the DHCP server 28 to renew their network addresses,the DSLAM module 64 adds the encapsulation information for these clientsto the DHCP messages 36 to continuously inform the BRAS device 26 of thetype of ATM encapsulation carried out on behalf of the subscribers 22.Further details will now be provided with reference to FIG. 3.

FIG. 3 is a detailed view 80 of the BRAS device 26. The BRAS device 26includes a network interface 82, a BRAS module 84, and a DHCP relayagent module 86. The DHCP relay agent module 86 corresponds to the DHCPrelay agent 36(B) in the BRAS device 26 (also see FIG. 1). The BRASmodule 84 is configured to perform BRAS operations such as aggregationand injection of IP QoS in Regional/Access Network portion of thenetwork 32 (also see FIG. 1). The DHCP relay agent 86 is configured toperform traditional DHCP relay agent operations (e.g., operate as anintermediate device between a DHCP client and a DHCP server for enhancedDHCP functionality) as well as obtain encapsulation information from theDHCP messages 42 and provide that encapsulation information to the BRASmodule 84. Communications between the BRAS module 84 and the DHCP relayagent module 86 is illustrated by arrows 88 and 90 in FIG. 3. Since theBRAS module 84 is the last IP aware device between the Regional/AccessNetwork portion and the customer network, the BRAS module 84 providescongestion management (i.e., synthesized IP QoS through the DSLAM device24) for maintained QoS at the CPE, i.e., the subscribers 22.

In some arrangements, the BRAS module 84 and the DHCP relay agent module86 operate on separate designated circuits within the BRAS device 26. Inother arrangements, the BRAS module 84 and the DHCP relay agent module86 run on the same circuitry (e.g., as different processes or threads onthe same set of processors). In all arrangements, the BRAS module 84 andthe DHCP relay agent module 86 are configured to communicate with eachother (e.g., via one or more internal communications buses, via one ormore inter-process communications schemes, via operating system and/orapplication programming interfaces, combinations thereof, etc.).

As further shown in FIG. 3, the DHCP relay agent 86 includes acontroller 92 and memory 94. The controller 92 is configured to extractthe encapsulation information from the DHCP communications exchange 42between the subscribers 22 (i.e., DHCP clients) and the DHCP server 28.The controller 92 stores this encapsulation information in the memory94. As a result, the BRAS module 84, is capable of controlling the flowof downstream communications passing through the BRAS and DSLAM devices24, 26 based on the encapsulation information.

In some arrangements, the encapsulation information is stored in thememory 94 as an entry of a database 96 of multiple entries 98. In thesearrangements, each entry 98 corresponds to a particular subscriber 22and the particular form of ATM overhead accounting carried out for thatsubscriber 22.

Furthermore, in some arrangements, the memory 94 and the database 96resides within and is managed by the BRAS module 84 rather than the DHCPrelay agent module 86. In these arrangements, the DHCP relay agentmodule 86 simply conveys the encapsulation information to the BRASmodule 84 as part of its communications 88, 90 (see FIG. 3) with theBRAS module 84.

It should be understood that the DHCP relay agent module 86 isconfigured to continue to provide the encapsulation information fromsubsequent DHCP communications 42 to the BRAS module 84 during IPaddress renewal operations. That is, when the subscribers 22 send newDHCP messages 38 to the DHCP server 28 to renew their network addresses,the DSLAM device 24 (FIG. 1) adds the encapsulation information forthese clients to the DHCP messages 38. The DHCP relay agent module 86(FIG. 3) then extracts this encapsulation information from the DHCPcommunications 42 (i.e., either the upstream DHCP messages 38 or thedownstream DHCP messages 40) to continuously inform the BRAS module 84of the type of ATM encapsulation carried out on behalf of thesubscribers 22.

At this point, it should be understood that there are differentoperating modes in which the DHCP relay agent module 86 is capable ofobtaining the encapsulation information from the DHCP messages 42. Inone operating mode, the DHCP relay agent module 86 is configured tosnoop the encapsulation information from upstream DHCP messages 38 fromthe DSLAM device 24 en route to the DHCP server 28. In another operatingmode, the DHCP relay agent module 86 is configured obtain theencapsulation information from the DHCP server 28 within downstream DHCPresponse messages 40 from the DHCP server 28. Further details of thesetwo different operating modes will now be provided with reference toFIGS. 4 and 5.

FIG. 4 is a flowchart of a procedure 100 performed by the BRAS device 26in accordance with a first operating mode in which the BRAS device 26snoops upstream DHCP messages 38. In step 102, the network interface 82of the BRAS device 26 receives a DHCP message 38 en route from aparticular subscriber 22 through the DSLAM device 24 to the DHCP server28. Recall that in the description above, the DSLAM device 24 isconfigured to add the type(s) of ATM encapsulation as Option 82information within the DHCP messages 38. The DHCP relay agent module 86of the BRAS device 26 then extracts the encapsulation information fromDHCP messages 38.

In step 104, the DHCP relay agent module 86 stores the encapsulationinformation in the memory 94. In some arrangements, the DHCP relay agentmodule 86 stores the encapsulation information as a database entry 98associated with the particular subscriber 22 (see the database 96 inFIG. 3).

In step 106, the BRAS module 84 of the BRAS device 26 then controls theflow of a downstream communication passing through the BRAS device 26and the DSLAM device 24 toward the subscriber 22 based on theencapsulation information stored in the memory 94. For example, the BRASmodule 84 is capable of throttling downstream traffic from other devices(see the device 30 in FIG. 1), dropping lower priority packets,combining or dividing packets, classifying and queuing packets, and soon, so that the subscribers 22 properly receive their prescribed QoS.Accordingly, the BRAS device 26 robustly and reliably shapes and policestraffic to maintain QoS for the subscriber 22.

FIG. 5 is a flowchart of a procedure 120 performed by the BRAS device 26in accordance with a second operating mode in which the BRAS device 26receives direction from the DHCP server through downstream DHCP messages40 (FIG. 1). Prior to operation, the DHCP server 28 is configured torespond to DHCP messages 38, which have been specially marked by theBRAS device 26, with directions for handling ATM overhead accounting.Accordingly, the BRAS device 26 marks upstream DHCP messages 38 (e.g.,using the Option 82 relay agent information feature) and then awaitsdirection from the DHCP server 28, such directions being piggy-backed onthe downstream DHCP responses.

In step 122, the network interface 82 of the BRAS device 26 receives aDHCP message 40 en route from the DHCP server 28 back to a particularsubscriber 22 in response to an earlier DHCP request message 38. Inparticular, the subscriber 22 sent that DHCP request message 38 upstreamto obtain an assigned network address 34 from the DHCP server 28. Asthat DHCP request message 38 traveled upstream through the DSLAM device24, the DSLAM device 24 added encapsulation information as Option 82information to the DHCP request message 38. The DHCP server 28 thengenerated the DHCP response message 40 and provided furtherencapsulation information within the DHCP response message 40 (e.g., asOption 82 information) to direct the BRAS device 26. Accordingly, theDHCP relay agent module 86 of the BRAS device 26 then extracts theencapsulation information from DHCP messages 40.

In step 124, the DHCP relay agent module 86 stores the encapsulationinformation in the memory 94 in a manner similar to that described abovein connection with FIG. 4. For example, in some arrangements, the DHCPrelay agent module 86 stores the encapsulation information as a databaseentry 98 associated with the particular subscriber 22 (see the database96 in FIG. 3).

In step 126, the BRAS module 84 of the BRAS device 26 then controls theflow of a downstream communication passing through the BRAS device 26and the DSLAM device 24 toward the subscriber 22 based on theencapsulation information stored in the memory 94. For instance, oncethe subscriber 22 is operational and begins acquiring content from otherdevices 30 through the network 32, the BRAS module 84 is capable ofthrottling packets, dropping lower priority packets, combining ordividing packets, classifying and queuing packets, and so on so that thesubscribers 22 properly receive their prescribed QoS. As a result, theBRAS device 26 robustly and reliably shapes and polices traffic tomaintain QoS for the subscriber 22.

FIG. 6 illustrates an exemplary DHCP exchange involving the variousdevices 22, 24, 26, 28 of the system 20 over time. As shown in FIG. 6,the DSLAM device 24 adds the type of ATM encapsulation as DHCP relayagent information, i.e., represented in FIG. 6 as OPT-82-ENCAPS, withinan upstream DHCP message 38. The BRAS device 26 adds further DHCP relayagent information indicating to the DHCP server 28 that the zBRAS device26 requests direction as to how to perform ATM overhead accounting fordownstream traffic, i.e., represented in FIG. 6 as OPT-82-QOS-REQ.

In the return direction, the DHCP server 28 replaces the DHCP relayagent information of the BRAS device 26 with direction as to how toperform ATM overhead accounting for downstream traffic, i.e.,represented in FIG. 6 as OPT-82-ENCAPS-FOR-BRAS. Such information iscapable of being added automatically by the DHCP server 28 (e.g., basedon a lookup procedure from a predefined table within the DHCP server 28)thus alleviating the need for a technician to manually configure theBRAS device 26. Next, the BRAS device 26 extracts the direction from theDHCP server 28 and subsequently shapes and polices traffic passingthrough the BRAS device 26 and the DSLAM device 24 en route to thesubscriber 22 based on this direction.

As described above, embodiments of the invention are directed totechniques for automatically controlling operation of a BRAS device 26based on encapsulation information (e.g., an identifier of the type ortypes of encapsulation) obtained from communications flowing through aDSLAM device 24 and the BRAS device 26. Such encapsulation informationis easily acquired (e.g., through monitoring of DHCP messages 42) thusremoving the burden of configuring the BRAS device 26 manually (e.g., bya technician) in order to account for encapsulation overhead.

While various embodiments of the invention have been particularly shownand described, it will be understood by those skilled in the art thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

1. A method to control operation of a Broadband Remote Access Server(BRAS) device, the method comprising: extracting encapsulationinformation from a communications exchange between a Customer PremisesEquipment (CPE) device and an external server device, the communicationsexchange passing through the BRAS device and a Digital Subscriber LineAccess Multiplexer (DSLAM) device; storing the encapsulation informationin local memory of the BRAS device; controlling a flow of a downstreamcommunication passing through the BRAS device and the DSLAM devicetoward the CPE device based on the encapsulation information stored inthe local memory of the BRAS device; wherein the external server deviceis a DHCP server; wherein the CPE device is an end-user device; whereinthe DSLAM device is disposed between the end-user device and the BRASdevice; wherein extracting the encapsulation information from thecommunications exchange between the CPE device and the external serverdevice includes: reading, by the BRAS device, contents from a portion ofa DHCP message which is en route from the DHCP server to the end-userdevice through the BRAS device and subsequently the DSLAM device toassign an Internet Protocol (IP) address to the end-user device, thecontents indicating that the end-user device and the DSLAM device areconstructed and arranged to exchange Transmission ControlProtocol/Internet Protocol (TCP/IP) packets by (i) encapsulatingportions of the TCP/IP packets within series of Asynchronous TransferMode (ATM) cells and (ii) exchanging the series of ATM cells, having theencapsulated portions of the TCP/IP packets therein, over a DigitalSubscriber Line disposed between the end-user device and the DSLAMdevice; receiving, at the BRAS device, a set of TCP/IP packets from aTCP/IP packet source which is different than the DHCP server, the set ofTCP/IP packets being en route from the TCP/IP packet source to theend-user device through the BRAS device and subsequently the DSLAMdevice; and incrementally outputting each TCP/IP packet of the set ofTCP/IP packets at a predetermined data rate to direct the DSLAM device,when (i) dividing the TCP/IP packets into portions, (ii) encapsulatingthose portions within a stream of ATM cells, and sending the stream ofATM cells to the end-user device through the Digital Subscriber Line, toprovide a Quality of Service at the particular data rate to theend-user.
 2. A method as in claim 1 wherein the external server deviceis configured to operate as a Dynamic Host Configuration Protocol (DHCP)server; and wherein extracting the encapsulation information includes:obtaining the encapsulation information from a DHCP message sent betweenthe CPE device and the DHCP server through the DSLAM device and the BRASdevice.
 3. A method as in claim 2 wherein obtaining the encapsulationinformation from the DHCP message includes: reading contents of a DHCPOption 82 portion of the DHCP message, the contents identifying one of avariety of encapsulation protocols.
 4. A method as in claim 3 whereinreading the contents of the DHCP Option 82 portion of the DHCP messageincludes: identifying, based on the contents of the DHCP Option 82portion of the DHCP message, a particular encapsulation protocolemployed by the DSLAM device on communications between the DSLAM deviceand the CPE device.
 5. A method as in claim 3 wherein the contents ofthe DHCP Option 82 includes data added by a DHCP relay agent running onthe DSLAM device; and wherein reading the contents of the DHCP Option 82portion of the DHCP message includes: acquiring the data added by theDHCP relay agent running on the DSLAM device.
 6. A method as in claim 3wherein the contents of the DHCP Option 82 includes information added bythe DHCP server in response to data provided by a DHCP relay agentrunning on the DSLAM device; and wherein reading the contents of theDHCP Option 82 portion of the DHCP message includes: acquiring theinformation added by the DHCP server in response to the data provided bya DHCP relay agent running on the DSLAM device.
 7. A method as in claim3 wherein the local memory of the BRAS device holds a database having aset of entries corresponding to a set of subscribers; wherein storingthe encapsulation information in the local memory of the BRAS deviceincludes saving the encapsulation information in a particular entry ofthe set of entries of the database; and wherein controlling the flow ofthe downstream communication includes: automatically adjusting bandwidthof the downstream communication based on the encapsulation informationin the particular entry of the set of entries of the database.
 8. ABroadband Remote Access Server (BRAS) device, comprising: a networkinterface; local memory; and a controller coupled to the networkinterface and the local memory, the controller being configured to:extract encapsulation information from a communications exchange betweena Customer Premises Equipment (CPE) device and an external serverdevice, the communications exchange passing through (i) the networkinterface of the BRAS device and (ii) a Digital Subscriber Line AccessMultiplexer (DSLAM) device, store the encapsulation information in thelocal memory, and control a flow of a downstream communication passingthrough (i) the network interface of the BRAS device and (ii) the DSLAMdevice toward the CPE device based on the encapsulation informationstored in the local memory; wherein the external server device is a DHCPserver; wherein the CPE device is an end-user device; wherein the DSLAMdevice is disposed between the end-user device and the BRAS device;wherein the controller, when extracting the encapsulation informationfrom the communications exchange between the CPE device and the externalserver device, is configured to: read contents from a portion of a DHCPmessage which is en route from the DHCP server to the end-user devicethrough the BRAS device and subsequently the DSLAM device to assign anInternet Protocol (IP) address to the end-user device, the contentsindicating that the end-user device and the DSLAM device are constructedand arranged to exchange Transmission Control Protocol/Internet Protocol(TCP/IP) packets by (i) encapsulating portions of the TCP/IP packetswithin series of Asynchronous Transfer Mode (ATM) cells and (ii)exchanging the series of ATM cells, having the encapsulated portions ofthe TCP/IP packets therein, over a Digital Subscriber Line disposedbetween the end-user device and the DSLAM device; and wherein thecontroller is further configured to: receive a set of TCP/IP packetsfrom a TCP/IP packet source which is different than the DHCP server, theset of TCP/IP packets being en route from the TCP/IP packet source tothe end-user device through the BRAS device and subsequently the DSLAMdevice; and incrementally output each TCP/IP packet of the set of TCP/IPpackets at a predetermined data rate to direct the DSLAM device, when(i) dividing the TCP/IP packets into portions, (ii) encapsulating thoseportions within a stream of ATM cells, and sending the stream of ATMcells to the end-user device through the Digital Subscriber Line, toprovide a Quality of Service at the particular data rate to theend-user.
 9. A BRAS device as in claim 8 wherein the external serverdevice is configured to operate as a Dynamic Host Configuration Protocol(DHCP) server; and wherein the controller, when extracting theencapsulation information, is configured to: obtain the encapsulationinformation from a DHCP message sent between the CPE device and the DHCPserver through the DSLAM device and the BRAS device.
 10. A BRAS deviceas in claim 9 wherein the controller, when obtaining the encapsulationinformation from the DHCP message, is configured to: read contents of aDHCP Option 82 portion of the DHCP message, the contents identifying oneof a variety of encapsulation protocols.
 11. A BRAS device as in claim10 wherein the controller, when reading the contents of the DHCP Option82 portion of the DHCP message, is configured to: identify, based on thecontents of the DHCP Option 82 portion of the DHCP message, a particularencapsulation protocol employed by the DSLAM device on communicationsbetween the DSLAM device and the CPE device.
 12. A BRAS device as inclaim 10 wherein the contents of the DHCP Option 82 includes data addedby a DHCP relay agent running on the DSLAM device; and wherein thecontroller, when reading the contents of the DHCP Option 82 portion ofthe DHCP message, is configured to: acquire the data added by the DHCPrelay agent running on the DSLAM device.
 13. A BRAS device as in claim10 wherein the contents of the DHCP Option 82 includes information addedby the DHCP server in response to data provided by a DHCP relay agentrunning on the DSLAM device; and wherein the controller, when readingthe contents of the DHCP Option 82 portion of the DHCP message, isconfigured to: acquire the information added by the DHCP server inresponse to the data provided by a DHCP relay agent running on the DSLAMdevice.
 14. A BRAS device as in claim 10 wherein the local memory of theBRAS device holds a database having a set of entries corresponding to aset of subscribers; wherein the controller, when storing theencapsulation information in the local memory of the BRAS device, isconfigured to save the encapsulation information in a particular entryof the set of entries of the database; and wherein the controller, whencontrolling the flow of the downstream communication, is configured toautomatically adjust bandwidth of the downstream communication based onthe encapsulation information in the particular entry of the set ofentries of the database.
 15. A BRAS device as in claim 14 wherein thecontroller, when automatically adjusting the bandwidth of the downstreamcommunication, is configured to: perform asynchronous transfer mode(ATM) overhead accounting and shaping of the downstream communication tooptimize traffic between the DSLAM device and the CPE device.
 16. A BRASdevice as in claim 14 wherein the controller is further configured to:obtain updated encapsulation information from a DHCP lease renewalexchange between the CPE device and the DHCP server; and update theparticular entry of the set of entries of the database based on theupdated encapsulation information.
 17. A Broadband Remote Access Server(BRAS) device, comprising: a network interface; local memory; and acontroller coupled to the network interface and the local memory, thecontroller including: means for extracting encapsulation informationfrom a communications exchange between a Customer Premises Equipment(CPE) device and an external server device, the communications exchangepassing through (i) the network interface of the BRAS device and (ii) aDigital Subscriber Line Access Multiplexer (DSLAM) device, means forstoring the encapsulation information in the local memory, and means forcontrolling a flow of a downstream communication passing through (i) thenetwork interface of the BRAS device and (ii) the DSLAM device towardthe CPE device based on the encapsulation information stored in thelocal memory; wherein the external server device is a DHCP server;wherein the CPE device is an end-user device; wherein the DSLAM deviceis disposed between the end-user device and the BRAS device; wherein themeans for extracting the encapsulation information from thecommunications exchange between the CPE device and the external serverdevice includes: means for reading contents from a portion of a DHCPmessage which is en route from the DHCP server to the end-user devicethrough the BRAS device and subsequently the DSLAM device to assign anInternet Protocol (IP) address to the end-user device, the contentsindicating that the end-user device and the DSLAM device are constructedand arranged to exchange Transmission Control Protocol/Internet Protocol(TCP/IP) packets by (i) encapsulating portions of the TCP/IP packetswithin series of Asynchronous Transfer Mode (ATM) cells and (ii)exchanging the series of ATM cells, having the encapsulated portions ofthe TCP/IP packets therein, over a Digital Subscriber Line disposedbetween the end-user device and the DSLAM device; and wherein thecontroller further includes: means for receiving a set of TCP/IP packetsfrom a TCP/IP packet source which is different than the DHCP server, theset of TCP/IP packets being en route from the TCP/IP packet source tothe end-user device through the BRAS device and subsequently the DSLAMdevice; and means for incrementally output each TCP/IP packet of the setof TCP/IP packets at a predetermined data rate to direct the DSLAMdevice, when (i) dividing the TCP/IP packets into portions, (ii)encapsulating those portions within a stream of ATM cells, and sendingthe stream of ATM cells to the end-user device through the DigitalSubscriber Line, to provide a Quality of Service at the particular datarate to the end-user.
 18. A method to control operation of a DigitalSubscriber Line Access Multiplexer (DSLAM) device, the methodcomprising: operating a DSLAM module within the DSLAM device; obtaininga type of encapsulation carried out by the DSLAM module; and identifyingthe type of encapsulation in encapsulation information within acommunications exchange between a Customer Premises Equipment (CPE)device and an external server device, the communications exchangepassing through the DSLAM device and through a Broadband Remote AccessServer (BRAS) device en route to an external server device; wherein theexternal server device is configured to operate as a Dynamic HostConfiguration Protocol (DHCP) server; and wherein identifying the typeof encapsulation in encapsulation information within the communicationsexchange between the CPE device and the external server device includes:inserting the encapsulation information into a DHCP message sent fromthe CPE device toward the DHCP server through the DSLAM device and theBRAS device; wherein the CPE device is an end-user device; wherein theDSLAM device is disposed between the end-user device and the BRASdevice; wherein inserting the encapsulation information into the DHCPmessage sent from the end-user device toward the DHCP server through theDSLAM device and the BRAS device includes inserting the encapsulationinformation in a form that allows: reading, by the BRAS device, contentsfrom a portion of a DHCP message which is en route from the DHCP serverto the end-user device through the BRAS device and subsequently theDSLAM device to assign an Internet Protocol (IP) address to the end-userdevice, the contents indicating that the end-user device and the DSLAMdevice are constructed and arranged to exchange Transmission ControlProtocol/Internet Protocol (TCP/IP) packets by (i) encapsulatingportions of the TCP/IP packets within series of Asynchronous TransferMode (ATM) cells and (ii) exchanging the series of ATM cells, having theencapsulated portions of the TCP/IP packets therein, over a DigitalSubscriber Line disposed between the end-user device and the DSLAMdevice; receiving, at the BRAS device, a set of TCP/IP packets from aTCP/IP packet source which is different than the DHCP server, the set ofTCP/IP packets being en route from the TCP/IP packet source to theend-user device through the BRAS device and subsequently the DSLAMdevice; and incrementally outputting, by the BRAS device, each TCP/IPpacket of the set of TCP/IP packets at a predetermined data rate todirect the DSLAM device, when (i) dividing the TCP/IP packets intoportions, (ii) encapsulating those portions within a stream of ATMcells, and sending the stream of ATM cells to the end-user devicethrough the Digital Subscriber Line, to provide a Quality of Service atthe particular data rate to the end-user.
 19. A Digital Subscriber LineAccess Multiplexer (DSLAM) device, comprising: a network interface; aDSLAM module; and an agent module coupled to the network interface andthe DSLAM module, the agent module being configured to (i) obtain a typeof encapsulation carried out by the DSLAM module, and (ii) identify thetype of encapsulation in encapsulation information within acommunications exchange between a Customer Premises Equipment (CPE)device and an external server device, the communications exchangepassing through the DSLAM device and through a Broadband Remote AccessServer (BRAS) device en route to an external server device; wherein theexternal server device is configured to operate as a Dynamic HostConfiguration Protocol (DHCP) server; and wherein the agent module, whenidentifying the type of encapsulation in the encapsulation informationwithin the communications exchange between the CPE device and theexternal server device, is configured to insert the encapsulationinformation into a DHCP message sent from the CPE device toward the DHCPserver through the DSLAM device and the BRAS device; wherein the CPEdevice is an end-user device; wherein the DSLAM device is disposedbetween the end-user device and the BRAS device; wherein the agentmodule configured to insert the encapsulation information into the DHCPmessage sent from the end-user device toward the DHCP server through theDSLAM device and the BRAS device includes being configured to insert theencapsulation information in a form that allows: reading, by the BRASdevice, contents from a portion of a DHCP message which is en route fromthe DHCP server to the end-user device through the BRAS device andsubsequently the DSLAM device to assign an Internet Protocol (IP)address to the end-user device, the contents indicating that theend-user device and the DSLAM device are constructed and arranged toexchange Transmission Control Protocol/Internet Protocol (TCP/IP)packets by (i) encapsulating portions of the TCP/IP packets withinseries of Asynchronous Transfer Mode (ATM) cells and (ii) exchanging theseries of ATM cells, having the encapsulated portions of the TCP/IPpackets therein, over a Digital Subscriber Line disposed between theend-user device and the DSLAM device; receiving, at the BRAS device, aset of TCP/IP packets from a TCP/IP packet source which is differentthan the DHCP server, the set of TCP/IP packets being en route from theTCP/IP packet source to the end-user device through the BRAS device andsubsequently the DSLAM device; and incrementally outputting, by the BRASdevice, each TCP/IP packet of the set of TCP/IP packets at apredetermined data rate to direct the DSLAM device, when (i) dividingthe TCP/IP packets into portions, (ii) encapsulating those portionswithin a stream of ATM cells, and sending the stream of ATM cells to theend-user device through the Digital Subscriber Line, to provide aQuality of Service at the particular data rate to the end-user.
 20. ADSLAM device as in claim 19 wherein the agent module, when inserting theencapsulation information into the DHCP message sent from the CPE devicetoward the DHCP server through the DSLAM device and the BRAS device, isconfigured to: provide contents of a DHCP Option 82 portion of the DHCPmessage, the contents identifying one of a variety of encapsulationprotocols.
 21. A DSLAM device as in claim 20 wherein the agent module,when providing the contents of the DHCP Option 82 portion of the DHCPmessage, is configured to: indicate, within the contents of the DHCPOption 82 portion of the DHCP message, a particular encapsulationprotocol employed by the DSLAM device on communications between theDSLAM device and the CPE device.
 22. A Digital Subscriber Line AccessMultiplexer (DSLAM) device, comprising: a network interface; a DSLAMmodule; and an agent module coupled to the network interface and theDSLAM module, the agent module including: means for obtaining a type ofencapsulation carried out by the DSLAM module, and means for identifyingthe type of encapsulation in encapsulation information within acommunications exchange between a Customer Premises Equipment (CPE)device and an external server device, the communications exchangepassing through the DSLAM device and through a Broadband Remote AccessServer (BRAS) device en route to an external server device; wherein theexternal server device is configured to operate as a Dynamic HostConfiguration Protocol (DHCP) server; and wherein means for identifyingthe type of encapsulation in the encapsulation information within thecommunications exchange between the CPE device and the external serverdevice of the agent module includes means for inserting theencapsulation information into a DHCP message sent from the CPE devicetoward the DHCP server through the DSLAM device and the BRAS device;wherein the CPE device is an end-user device; wherein the DSLAM deviceis disposed between the end-user device and the BRAS device; wherein theagent module includes means for inserting the encapsulation informationinto the DHCP message sent from the end-user device toward the DHCPserver through the DSLAM device and the BRAS device includes beingconfigured to insert the encapsulation information in a form thatincludes: means for reading, by the BRAS device, contents from a portionof a DHCP message which is en route from the DHCP server to the end-userdevice through the BRAS device and subsequently the DSLAM device toassign an Internet Protocol (IP) address to the end-user device, thecontents indicating that the end-user device and the DSLAM device areconstructed and arranged to exchange Transmission ControlProtocol/Internet Protocol (TCP/IP) packets by (i) encapsulatingportions of the TCP/IP packets within series of Asynchronous TransferMode (ATM) cells and (ii) exchanging the series of ATM cells, having theencapsulated portions of the TCP/IP packets therein, over a DigitalSubscriber Line disposed between the end-user device and the DSLAMdevice; means for receiving, at the BRAS device, a set of TCP/IP packetsfrom a TCP/IP packet source which is different than the DHCP server, theset of TCP/IP packets being en route from the TCP/IP packet source tothe end-user device through the BRAS device and subsequently the DSLAMdevice; and means for incrementally outputting, by the BRAS device, eachTCP/IP packet of the set of TCP/IP packets at a predetermined data rateto direct the DSLAM device, when (i) dividing the TCP/IP packets intoportions, (ii) encapsulating those portions within a stream of ATMcells, and sending the stream of ATM cells to the end-user devicethrough the Digital Subscriber Line, to provide a Quality of Service atthe particular data rate to the end-user.